1. Field of the Invention
This invention relates to fiber blends for wearing apparel and is directed more particularly to a fiber blend for use in protective clothing to provide multifunctional protection to a wearer.
2. Description of the Prior Art
Combat uniform fabrics have been woven from yarns made from a staple blend of cotton and nylon fibers. This fiber blend supports dyeing and printing using a combination of acid and vat dyes to impart a camouflage pattern providing both visual and near infrared camouflage protection. This cotton and nylon fiber blend yarn, in combination with a lightweight, thin fabric construction, has consistently provided protection, comfort, durability, and UV resistance for US military service personnel for more than twenty years. Many efforts have been undertaken to integrate flame and thermal protection into this fabric, with little success. Novel fibers, fiber blends and functional finishes previously investigated include BASOFIL® melamine, Flame Retardant-Treated (FRT) cotton, FRT cotton/nylon, FRT TENCEL® rayon, FRT cotton/KEVLAR® para-aramid/nylon, carbonized rayon/NOMEX Meta-Aramid®, KEVLAR® para-aramid/Flame Resistant (FR) rayon, NOMEX® meta-aramid/FR rayon, polybenzimidazole (PBI) and PBI/FRT cotton.
Many of the inherently flame resistant fibers have been found unacceptable for use in a homogeneous fabric because of high cost and the requirement for visual and near infrared camouflage. The high polymer orientation of aramids and PBI, for example, contributes to flame resistance, but reduces or eliminates their ability to be dyed with traditional dyestuffs because of the lack of chemical dye sites. Some of these materials achieve coloration by pigment injection in solution form, but their versatility is limited. Aramid blends can be dyed and camouflage printed using proprietary technology, but that adds significantly to the final cost of the finished fabric. Still prized for their inherent flame resistance, some of these fibers have been blended with low cost fibers to reduce the overall cost of the fabric. Flame retardant rayon, which is inherently flame resistant, rather than flame retardant treated, has been blended with aramids in 60/40 and 35/65 percent blend ratios, but these materials have fallen short of the desired fabric strength, and camouflage print thereon has demonstrated poor colorfastness.
Flame-retardant treated cotton has long been the industry standard for use in low cost flame resistant industrial work wear. However, some treatments add 20 percent to the weight of the fabric. Flame-retardant treated cotton has been blended with nylon in 88/12 percent blend ratios, wherein the nylon was added to improve strength. While the addition of the small amount of nylon does not negatively impact flame resistance, a heavier weight fabric of 11 ounces/yard2 is required to achieve relatively acceptable breaking and tearing strengths.
Flame-retardant treated cotton has also been blended with KEVLAR® para-aramid and nylon to enhance flame resistance, prevent break through and improve abrasion resistance in a 58 percent cotton, 27 percent KEVLAR® para-aramid, 15 percent nylon blend ratio. While the KEVLAR® para-aramid is the strongest of the three fibers, it must occupy less than 50 percent of the total material composition to keep costs at an acceptable level, and not interfere with the application of camouflage print dyes which are compatible only with the cotton fiber. The strength of the fabric is dictated by the dominant fiber, which in this case is the lower strength cotton. In addition, the high end and pick count required to anchor the KEVLAR® para-aramid fiber detrimentally reduces the fabric tearing strength to three pounds in the warp and filling directions. PBI has been blended with flame-retardant treated cotton in 20/80 percent blend ratio in 5.0 and 6.6 ounce/yard2 weights; however, the unsatisfactory performance characteristics of the predominant fiber, cotton, prevail.
BASOFIL® melamine fiber has demonstrated low fiber tenacity and developmental efforts have been directed toward insulation, knitted headwear, hand wear, and underwear applications, where high strength is not a critical factor. Blends of carbonized rayon and NOMEX® meta-aramid have been investigated and while they have demonstrated good strength performance they can not be dyed and camouflage printed. Flame-retardant treated TENCEL® rayon demonstrates good strength, but the camouflage thereof has demonstrated poor colorfastness.
Core spun yarns have been investigated and developed with the intent of manufacturing a yarn with a high strength inherently flame resistant core, and low cost readily camouflage printable sheath fiber. The best performing material combination was found to be a cotton sheath, KEVLAR® para-aramid core yarn. However, these materials have also fallen short on strength because only the KEVLAR® para-aramid-based core and not the sheath contributed to the fabric strength.
Low cost, flame resistant wool has been blended with meta-aramid, para-aramid and electrostatic dissipative fiber and various methods have been investigated to identify the most cost effective dyeing and finishing methods to produce the best performing fabric. Various fabrics have been developed and evaluated, including those with producer colored and dyeable meta-aramid fiber, with and without an enzyme treatment to remove wool scales, piece dyed and overprinted, and a group that was printed only. The best performing lowest cost fabric was made from undyed meta-aramid and wool that had not been enzyme treated.
Print options have been investigated. In one, the fabric was first dyed to one of the lighter colors and then overprinted with the darker color screens. In another, the fabric was not dyed and all of the three required colors were printed on the undyed fabric. Dyeing prior to printing has not increased either color yield or the colorfastness properties of the printed fabrics and the fabric has lost strength. Printing directly on the undyed fabric results in better fabric mechanical properties and reduces costs by eliminating an additional manufacturing process. The aramid and wool blend fabric has demonstrated acceptable visual shade and camouflage protection. A fabric that had not been enzyme treated met the performance goals for near infrared camouflage for the colors in the Universal Camouflage Pattern.
Thus, while many of the developmental materials investigated have met fabric flame resistance goals (ASTM D 6413; 2.0 seconds, maximum after flame; 25.0 seconds, maximum after glow; 4.0 inches maximum char length), strength and other performance requirements, such as colorfastness of the camouflage, have fallen short.
An object of the invention is, therefore, to provide a preferred embodiment comprising a fiber blend, a yarn, and a fabric which afford multifunctional protection to a wearer, including flame and thermal protection, UV resistance, electrostatic dissipation, and which accept camouflage coloration and exhibit color fastness to provide visual and near infrared camouflage protection. Another embodiment provides no electrostatic dissipation protection.
Further objects of the invention include the provision of such a fiber blend, yarn and fabric of high strength and durability, but of light weight and comfortable to wear, all at low cost.
Still further objects of the invention include the provision of such a fiber blend, yarn and fabric amenable to treatment with water repellent, oil repellent and insect repellent.